The present invention relates to floor maintenance machines in general, and in particular to a safety interlock for controlling start up of a floor maintenance machine of a type having a rotatable floor treating pad or brush.
A floor maintenance machine of a type having a rotatable floor treating element, such as a pad or brush, and a motor positioned over the element, can be a potentially dangerous piece of equipment, particularly when operated by an untrained or careless user. since the weight of the motor is directly over the element and only the element touches the floor during operation, the machine handle attempts to rotate when held, and has a reaction torque equal to that imposed by the spinning element. If the handle is held so that the element sits squarely on the floor, when the machine is operating it can be balanced and held stationary with very little effort. However, if the machine is started from rest without securely holding onto the handle, the handle will whip around the element and motor and injury to an operator can occur.
In an effort to eliminate or at least minimize handle reaction torque, machines have been designed that do not have the motor over the floor treating element. However, a disadvantage is that the design comprises the function and utility of the machine, since it does not permit the machine to perform as efficiently as one in which the motor is over the element.
To avoid sacrificing performance, most efforts to make floor maintenance machines safer have been directed to using a separate safety device, which usually is a button or lever that must be depressed or moved to free a hand lever to be squeezed to start the machine. The approach eliminates accidental start up, since brushing up against or bumping the hand lever will not cause the machine to start. Rather, before it can be started a deliberate action is required, i.e., releasing the safety sevice.
Unfortunately, such conventionally employed safety devices address only one safety aspect. They prevent accidental start up of the machine, but they do not protect the untrained or careless user upon start up. The problem arises because almost all floor maintenance machines have dual hand levers, and can be started up and operated using either the right or the left hand. This is done to prevent fatigue, allow for line cord movement, permit spraying a cleaner on the floor, etc. Because of this, conventional safety devices are designed so that they must be operated by the hand not on a hand lever, or by the hand on a hand lever while the other hand is not on the other hand lever. Either condition can be dangerous, since the high reaction torque upon machine start up can pull the machine handle out of the user's one hand.